Low-lithium-content silicon-based negative electrode material, preparation method thereof, negative electrode and lithium ion battery

Abstract

The present disclosure relates to a low lithium content silicon-based negative electrode material and a preparation method thereof, a negative electrode and a lithium ion battery, the method comprising the following steps: S1, mixing metal lithium and porous silicon-containing powder, and then performing solid-phase homogenization treatment under an inert atmosphere to obtain a first mixture; wherein the mass ratio of metal lithium to silicon-containing powder is 1:(10-120); S2, adding a solid dispersant to the first mixture for dispersion homogenization treatment to obtain a second mixture; S3, adding a carbon source to the second mixture for carbon-coated homogenization treatment to obtain a low lithium content silicon-based negative electrode material precursor; S4, performing sintering treatment on the low lithium content silicon-based negative electrode material precursor; wherein steps S1-S4 are performed under an inert atmosphere. The first coulomb efficiency and cycle stability of the lithium ion battery can be significantly improved.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to lithium ion battery materials, in particular, to a low-lithium-content silicon-based anode material and a preparation method thereof, an anode and a lithium ion battery. BACKGROUND

[0002] The rapid development of portable electronic products and new energy power vehicles puts forward higher requirements on the energy density and cycle life of the next generation of lithium ion batteries, and high-energy-density lithium ion batteries are the main development direction in the future. The improvement of the energy density of the battery mainly depends on the development of key electrode materials, such as the continuous improvement of the capacity of the positive and negative electrode materials. The current commercial anode material is graphite, and the theoretical specific capacity is 372 mAh g -1 , which cannot meet the needs of high-energy-density batteries. In order to meet the energy needs of the new generation and improve the energy density of the battery, it is of great significance to develop new lithium battery anode materials.

[0003] Among the new anode materials, silicon materials are attracting attention because of their high theoretical capacity, abundant reserves, and low discharge voltage. However, silicon materials undergo a large volume expansion (>300%) during lithium extraction and insertion, which causes the anode material to pulverize and fall off, forming "dead silicon" and ultimately leading to the loss of electrical contact of the anode material and the failure of the battery. In addition, repeated volume expansion and contraction also lead to the continuous destruction of the SEI film on the surface, which continuously consumes Li + from the positive electrode, resulting in a decrease in the coulombic efficiency of the battery. These problems ultimately lead to a sharp deterioration in the cycle performance of the battery, seriously affecting the service life of the battery.

[0004] Nanocrystallization of silicon materials is an effective method widely used in academia and industry to solve the problem of volume expansion of silicon materials and improve the cycle stability. However, silicon is easily oxidized during nanocrystallization, forming silicon oxide on the surface, which leads to the consumption and loss of a large amount of lithium ions during the first cycle, resulting in a decrease in the first coulombic efficiency. By pre-lithiating the silicon material during preparation, lithium and silicon react with the surface oxide layer during nanocrystallization to form lithium oxide, which can solve the problem of decreased first coulombic efficiency caused by surface oxidation of silicon / silicon-based materials. In addition, some lithium can be reserved in the silicon-based material, which can supplement lithium during the charge and discharge cycle of the silicon-based material, reduce the consumption and loss of lithium ions during the battery cycle, and improve the capacity retention rate.

[0005] Currently, the pre-lithiation technology is mainly applied to the preparation of silicon / silicon-based materials, mainly including lithium-organic solvent liquid phase pre-lithiation, pre-lithiation additives, addition of stable metal lithium powder to the pole piece, electrochemical pre-lithiation, and contact short-circuit reaction. However, the above pre-lithiation methods have poor compatibility with the existing battery system and poor operability. For example, the pole piece electrochemical lithiation requires additional lithiation technology process and discharge equipment, and the chemical lithiation generally requires active lithium reagent, long lithiation time or liquid phase high temperature condition to achieve the optimal physicochemical depth, and the operability is not strong. SUMMARY

[0006] The purpose of the present disclosure is to provide a low-lithium-content silicon-based negative electrode material and a preparation method thereof, a negative electrode and a lithium ion battery, which can significantly improve the initial coulomb efficiency and cycle stability of the lithium ion battery under the condition of low lithium content.

[0007] To achieve the above purpose, the first aspect of the present disclosure provides a method for preparing a low-lithium-content silicon-based negative electrode material, which comprises the following steps: S1, mixing metal lithium with porous silicon-containing powder, and then performing solid-phase homogenization treatment under an inert atmosphere to obtain a first mixture; wherein the mass ratio of metal lithium to silicon-containing powder is 1:(10-120); S2, adding a solid dispersant to the first mixture for dispersion homogenization treatment to obtain a second mixture; S3, adding a carbon source to the second mixture for carbon-coated homogenization treatment to obtain a low-lithium-content silicon-based negative electrode material precursor; S4, performing sintering treatment on the low-lithium-content silicon-based negative electrode material precursor; wherein steps S1-S4 are performed under an inert atmosphere.

[0008] Optionally, in step S1, the porous silicon-containing powder is selected from one or more of metallurgical silicon powder, micron silicon powder, nano silicon powder, alloy silicon powder, and silicon-carbon composite material powder; preferably, the average particle size of the porous silicon-containing powder is 0.2-50 μm, the average pore size is 1-50 nm, and the BET specific surface area is 0.5-100 m 2 / g; the metal lithium is selected from one or more of lithium ingot, lithium wire, lithium powder and lithium sheet; preferably, the mass ratio of the metal lithium to the silicon-containing powder is 1:(50-100).

[0009] Optionally, in step S1, the porous silicon-containing powder comprises one of micron silicon powder or silicon-carbon composite powder; optionally, the micron silicon powder is prepared by acid etching of a silicon alloy raw material; wherein the silicon alloy raw material is selected from any one or several of silicon-aluminum alloy, silicon-iron alloy, and silicon-magnesium alloy, and the average particle size of the silicon alloy raw material is 1-500 μm; the acid is selected from one or several of hydrochloric acid, nitric acid, and sulfuric acid; optionally, the silicon-carbon composite material is obtained by mechanical mixing of elemental silicon, a solvent, and an acid followed by high-temperature calcination; wherein the solvent is selected from one or several of isopropyl alcohol, ethanol, hexane, cyclohexane, and acetone; the acid is selected from one or several of citric acid, hydrochloric acid, nitric acid, and sulfuric acid; the average particle size of the elemental silicon is 30-100 μm; the mechanical mixing is performed using a sand mill for 4-48 hours; and the high-temperature calcination is performed under conditions including a temperature of 600-1200 °C and a time of 2-8 hours.

[0010] Optionally, in step S1, the solid-phase homogenization is performed by mechanical homogenization selected from any one of a ball mill, a sand mill, a homogenizer, or a disperser; optionally, in step S1, the solid-phase homogenization is performed at a rotation speed of 300-2000 r / min for a time of 6-72 h, and a ball-to-material ratio of (1-20):1.

[0011] Optionally, in step S2, the solid dispersant is selected from one or several of natural graphite, artificial graphite, mesocarbon microbeads, hard carbon, and soft carbon; and the mass ratio of the solid dispersant to the metal lithium is (5-100):1, preferably (5-50):1.

[0012] Optionally, in step S2, the dispersion homogenization is performed by mechanical homogenization selected from any one of a ball mill, a sand mill, a homogenizer, or a disperser; the dispersion homogenization is performed at a rotation speed of 50-500 r / min for a time of 0.5-12 h, and a ball-to-material ratio of (1-50):1.

[0013] Optionally, in step S3, the carbon source is selected from one or several of a polymeric carbon source, a petroleum-based carbon source, a saccharide carbon source, a graphite-based carbon source, and other carbon sources; the polymeric carbon source comprises one or several of phenolic resin, epoxy resin, polyvinylpyrrolidone, and polyvinyl alcohol; the petroleum-based carbon source comprises one or several of pitch, petroleum coke, and needle coke; the saccharide carbon source comprises one or several of glucose, sucrose, and fructose; the graphite-based carbon source comprises one or both of natural graphite and artificial graphite; the other carbon source comprises one or several of mesocarbon microbeads, hard carbon, and soft carbon; and the mass ratio of the metal lithium to the carbon source is 1:(5-100), preferably 1:(5-50).

[0014] Optionally, in step S3, the homogenization treatment by carbon coating includes mechanical homogenization selected from any one of a ball mill, a sand mill, a homogenizer or a disperser; the rotation speed of the mechanical homogenization is 100-500 r / min, the time is 0.5-12 h, and the ball-to-material ratio is (10-30):1.

[0015] Optionally, in step S4, the sintering treatment includes a first-stage sintering and a second-stage sintering; the first-stage sintering has a temperature of 200-500 ℃, a temperature rising rate of 0.5-2 ℃ / min, and a constant temperature time of 1-6 h; the second-stage sintering has a temperature of 600-1200 ℃, a temperature rising rate of 0.5-5 ℃ / min, and a constant temperature time of 1-12 h; preferably, the first-stage sintering has a temperature of 300-450 ℃, a temperature rising rate of 1-1.5 ℃ / min, and a constant temperature time of 2-4 h; the second-stage sintering has a temperature of 700-900 ℃, a temperature rising rate of 2-6 ℃ / min, and a constant temperature time of 2-5 h.

[0016] Optionally, the inert atmosphere contains one or more of nitrogen, helium, neon, argon, krypton and xenon; the water content of the inert atmosphere is 0.1 wt% or less, and the oxygen content is 0.1 wt% or less.

[0017] The second aspect of the present disclosure provides a low-lithium-content silicon-based negative electrode material prepared by the method of the first aspect of the present disclosure.

[0018] The third aspect of the present disclosure provides a low-lithium-content silicon-based negative electrode material, which includes negative electrode material particles having a core-shell structure; the inner core of the negative electrode material particles includes a porous silicon matrix and a lithium-containing component dispersed on the surface of the silicon matrix, the lithium-containing component containing Li2O; the outer shell of the negative electrode material particles includes a carbon coating layer covering the inner core; wherein the total content of the lithium-containing component in the negative electrode material particles is 0.01-10 wt%.

[0019] Optionally, the total content of the lithium-containing component in the negative electrode material particles is 1-5 wt%; the content of the carbon coating layer in the negative electrode material particles is 5-50 wt%, preferably 15-50 wt%; further preferably, the lithium-containing component does not contain metallic lithium.

[0020] Optionally, the average particle size of the negative electrode material particles is 0.2-50 μm, the average pore size is 1-50 nm, the BET specific surface area is 0.5-100 m 2 / g; the thickness of the carbon coating layer is 1-500 nm.

[0021] The fourth aspect of the present disclosure provides a negative electrode of a lithium ion battery, which includes the low-lithium-content silicon-based negative electrode material of the second aspect or the third aspect of the present disclosure.

[0022] The fifth aspect of the present disclosure provides a lithium ion battery comprising the negative electrode of the fourth aspect of the present disclosure.

[0023] By the above technical solution, the present disclosure provides a low-lithium-content silicon-based negative electrode material, a preparation method thereof, a negative electrode, and a lithium ion battery. The present disclosure uses metal lithium and a porous silicon-based material as raw materials, reduces the amount of metal lithium, and realizes the introduction of lithium into the porous silicon-containing powder by solid-phase homogenization treatment during the preparation process. The reaction of metal lithium and oxygen in the porous silicon-containing powder produces lithium oxide, realizes pre-lithium supplementation, avoids the reduction of the first coulomb efficiency caused by the oxidation of the silicon-containing powder during the preparation process, and simultaneously uses the lithium oxide as a buffer medium to buffer the volume expansion during the cycle process, making the material structure more stable. The introduction of a solid dispersant avoids the agglomeration and adhesion of the porous silicon-containing powder and lithium during the homogenization process, fully disperses the silicon-lithium particles, and forms a carbon coating layer on the surface of the particles by adding a carbon source for coating, further improving the cycle performance and stability of the negative electrode material. The present disclosure realizes the pre-lithium supplementation of the silicon-based material powder by a solid-phase homogenization one-step method, is compatible with the existing lithium ion battery assembly system, and can be directly applied to the existing lithium ion battery system. Meanwhile, the present disclosure has the characteristics of simple process, controllable lithium supplementation, environmentally friendly process, low cost, and being conducive to large-scale production.

[0024] Other features and advantages of the present disclosure will be described in detail in the following specific embodiments section. BRIEF DESCRIPTION OF DRAWINGS

[0025] The accompanying drawings are included to provide a further understanding of the present disclosure and constitute a part of the specification, and together with the following specific embodiments, serve to explain the present disclosure but do not constitute a limitation thereof. In the drawings:

[0026] Figure 1 A scanning electron microscope photo of the negative electrode material prepared for Example 1;

[0027] Figure 2 A transmission electron microscope photo of the negative electrode material prepared for Example 1;

[0028] Figure 3 An X-ray diffraction spectrum of the negative electrode material prepared for Example 1;

[0029] Figure 4 A Li 1s X-ray photoelectron high-resolution scanning energy spectrum of the negative electrode material prepared for Example 1;

[0030] Figure 5 A first charge-discharge curve of the battery prepared from the negative electrode material prepared for Example 2 at a current density of 0.2 C;

[0031] Figure 6The capacity retention curve of the battery prepared by using the negative electrode material prepared in Example 4 and the carbon-silicon composite material prepared in Comparative Example 3 as the negative electrode at a current density of 0.2C is shown in Figure 1.

[0032] Figure 7 The first charge-discharge curve of the battery prepared by using the negative electrode material DC1 prepared in Comparative Example 1 as the negative electrode at a current density of 0.2C is shown in Figure 2. DETAILED DESCRIPTION

[0033] The specific embodiments of the present disclosure are described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are merely intended to illustrate and explain the present disclosure, and are not intended to limit the present disclosure.

[0034] The first aspect of the present disclosure provides a method for preparing a low-lithium-content silicon-based negative electrode material for a lithium ion battery, which comprises the following steps:

[0035] S1, mixing metallic lithium with a porous silicon-containing powder, and then performing solid-phase homogenization treatment under an inert atmosphere to obtain a first mixture;

[0036] S2, adding a solid dispersant to the first mixture and performing dispersion homogenization treatment to obtain a second mixture;

[0037] S3, adding a carbon source to the second mixture and performing carbon-coating homogenization treatment to obtain a low-lithium-content silicon-based negative electrode material precursor;

[0038] S4, performing sintering treatment on the low-lithium-content silicon-based negative electrode material precursor;

[0039] Steps S1-S4 are performed under an inert atmosphere.

[0040] The method for preparing a low-lithium-content silicon-based negative electrode material for a lithium ion battery provided by the present disclosure uses metal lithium and a porous silicon-based material as raw materials, reduces the amount of metal lithium used, and realizes the introduction of lithium into the porous silicon-containing powder by solid-phase homogenization treatment during the preparation process. The metal lithium reacts with the oxygen in the porous silicon-containing powder to produce lithium oxide, thereby achieving pre-lithium supplementation and avoiding the reduction in the first coulomb efficiency caused by the oxidation of the silicon-containing powder during the preparation process. The lithium oxide acts as a buffer medium to buffer the volume expansion during the cycling process, making the material structure more stable. The introduction of a solid dispersant prevents the agglomeration and adhesion of the porous silicon-containing powder and lithium during the homogenization process, allowing the silicon-lithium particles to be fully dispersed. The addition of a carbon source forms a carbon coating layer on the surface of the particles, further improving the cycle performance and stability of the negative electrode material. The present disclosure realizes pre-lithium supplementation of silicon-based material powder by a one-step solid-phase homogenization method, is compatible with existing lithium ion battery assembly systems, and can be directly applied to existing lithium ion battery systems. The process is simple, lithium supplementation is controllable, the process is environmentally friendly, the cost is low, and it is conducive to large-scale production.

[0041] In one specific embodiment, the inert atmosphere in steps S1-S4 comprises one or more of nitrogen, helium, neon, argon, krypton, and xenon; the water content of the inert atmosphere is 0.1 wt% or less, and the oxygen content is 0.1 wt% or less.

[0042] In one preferred embodiment, the mass ratio of the metal lithium to the silicon-containing powder is 1:(50-100). According to the optimized mass ratio of metal lithium to silicon-containing powder in this embodiment, lithium can be further introduced, and the solid-phase homogenization reaction allows the metal lithium to react with the oxygen on the surface of the silicon-containing powder to produce lithium oxide, thereby avoiding the phenomenon of surface oxidation of the silicon-containing material to produce silicon oxide during the subsequent nanocrystallization process, which reduces the first coulomb efficiency.

[0043] In one embodiment, in step S1, the porous silicon-containing powder is selected from one or more of metallurgical silicon powder, micron silicon powder, nanosilicon powder, alloy silicon powder, and silicon-carbon composite material powder. The average particle size of the porous silicon-containing powder is 0.2-50 μm, the average pore size is 1-50 nm, and the BET specific surface area is 0.5-100 m 2 / g; preferably, the average particle size of the porous silicon-containing powder is 2-5 μm, the average pore size is 5-30 nm, and the BET specific surface area is 1-50 m 2 / g.

[0044] In one embodiment, the metal lithium is selected from one or more of lithium ingots, lithium wires, lithium powder, and lithium sheets.

[0045] In the present disclosure, the porous silicon-containing powder comprises one of micron silicon powder or silicon-carbon composite powder. The porous silicon-containing powder can be obtained through conventional purchase channels or prepared by any known preparation method. For example, the porous silicon-containing powder can be prepared by the following two specific preparation embodiments.

[0046] In one specific embodiment, the micron silicon powder is prepared by acid etching of a silicon alloy raw material; wherein the silicon alloy raw material is selected from any one or several of silicon-aluminum alloy, silicon-iron alloy, silicon-magnesium alloy, and the average particle size of the silicon alloy raw material is 1-500 μm; and the acid is selected from one or several of hydrochloric acid, nitric acid and sulfuric acid.

[0047] In another specific embodiment, the carbon-silicon composite material is obtained by mechanically mixing elemental silicon, a solvent and an acid followed by high-temperature calcination; wherein the solvent is selected from one or several of isopropyl alcohol, ethanol, hexane, cyclohexane and acetone; the acid is selected from one or several of citric acid, hydrochloric acid, nitric acid and sulfuric acid; the average particle size of the elemental silicon is 30-100 μm; the mechanical mixing is performed by sand mill for 4-48 hours; and the high-temperature calcination is performed under the conditions of temperature of 600-1200 °C and time of 2-8 hours.

[0048] In one embodiment, in step S1, the solid-phase homogenization treatment is performed by mechanical homogenization selected from any one of ball mill, sand mill, homogenizer or disperser.

[0049] Optionally, in step S1, the solid-phase homogenization treatment is performed at a rotation speed of 300-2000 r / min for a homogenization time of 6-72 h, and the ball-to-material ratio is (1-50):1; preferably, the rotation speed is 300-600 r / min, the homogenization time is 12-24 h, and the ball-to-material ratio is (10-20):1.

[0050] The solid-phase homogenization treatment provided by the present disclosure can make the metal lithium fully react with the oxygen on the surface of the silicon-containing material.

[0051] In one embodiment, in step S2, the solid dispersant is selected from one or several of natural graphite, artificial graphite, mesocarbon microbeads, hard carbon and soft carbon. The present disclosure can avoid the adhesion and agglomeration of silicon and lithium during the ball milling reaction by introducing the graphite-based solid dispersant, so as to fully disperse the silicon-lithium particles; at the same time, the dispersant can also form a dispersed conductive network to increase the particle conductivity and inhibit the decrease in conductivity caused by the introduction of lithium.

[0052] In one preferred embodiment, the mass ratio of the solid dispersant to the metal lithium is (5-100):1, preferably (5-50):1.

[0053] In one embodiment, in step S2, the dispersion and homogenization treatment is mechanical homogenization, which is selected from any one of a ball mill, a sand mill, a homogenizer or a disperser;

[0054] The dispersion and homogenization treatment has a rotation speed of 50-500 r / min, a time of 0.5-12 h, and a ball-to-material ratio of (1-50):1; preferably, the rotation speed is 250-400 r / min, the homogenization time is 2-5 h, and the ball-to-material ratio is (10-20):1.

[0055] In one embodiment, in step S3, the carbon source is selected from one or more of a polymer carbon source, a petroleum carbon source, a sugar carbon source, a graphite carbon source, and other carbon sources.

[0056] The polymer carbon source includes one or more of phenolic resin, epoxy resin, polyvinylpyrrolidone, and polyvinyl alcohol.

[0057] The petroleum carbon source includes one or more of pitch, petroleum coke, and needle coke.

[0058] The sugar carbon source includes one or more of glucose, sucrose, and fructose.

[0059] The graphite carbon source includes one or both of natural graphite and artificial graphite.

[0060] The other carbon source includes one or more of mesocarbon microbeads, hard carbon, and soft carbon.

[0061] Generally, after the pre-lithiation of the negative electrode material, the basicity of the material increases due to the introduction of lithium. When the negative electrode slurry is prepared, the molecular chains of the binder are cut off, resulting in low viscosity of the slurry, and even a reaction with the binder and / or solvent water, making it difficult to be slurried. In the process, the present disclosure introduces a carbon source for coating, forming a carbon coating layer on the surface of the silicon-lithium particles, which can avoid the reaction with the binder and / or solvent water during the preparation of the slurry; at the same time, the carbon coating layer can also protect the internal lithium from oxidation during the environmental transfer process; in addition, the carbon coating layer can further inhibit the decrease in electrical conductivity caused by the insertion of lithium, thereby improving the first coulombic efficiency and cycle stability of the battery made of the material.

[0062] In one embodiment, the mass ratio of the carbon source to the metal lithium is (5-100):1, preferably (5-50):1.

[0063] In one specific embodiment, in step S3, the carbon-coated homogenization treatment is mechanical homogenization, which is selected from any one of a ball mill, a sand mill, a homogenizer or a disperser.

[0064] The carbon-coated homogenization speed is 100-500 r / min, the time is 0.5-12 h, and the ball-to-material ratio is (10-30):1; preferably, the speed is 200-450 r / min, the homogenization time is 2-6 h, and the ball-to-material ratio is (15-20):1.

[0065] In one embodiment, in step S4, the sintering process comprises a first-stage sintering and a second-stage sintering, the first-stage sintering has a temperature of 200-500 ℃, a temperature rising rate of 0.5-2 ℃ / min, and a constant temperature time of 1-6 h; the second-stage sintering has a temperature of 600-1200 ℃, a temperature rising rate of 700-900 ℃ / min, and a constant temperature time of 1-12 h.

[0066] In a preferred embodiment, the first-stage sintering has a temperature of 300-450 ℃, a temperature rising rate of 1-1.5 ℃ / min, and a constant temperature time of 2-4 h; the second-stage sintering has a temperature of 700-900 ℃, a temperature rising rate of 2-6 ℃ / min, and a constant temperature time of 2-5 h.

[0067] The inventors of the present disclosure found that, by performing thermal stabilization through segmented temperature rising sintering and limiting the thermal stabilization temperature within the above range, the growth of silicon grains inside the silicon particles can be inhibited, and the cycle stability can be further prevented from decreasing.

[0068] The second aspect of the present disclosure provides a low-lithium-content silicon-based negative electrode material prepared by the method of the first aspect of the present disclosure.

[0069] The third aspect of the present disclosure provides a low-lithium-content silicon-based negative electrode material, which comprises negative electrode material particles having a core-shell structure, the inner core of the negative electrode material particles comprises a porous silicon matrix and a lithium-containing component dispersed on the surface of the silicon matrix, the lithium-containing component comprises Li2O; the outer shell of the negative electrode material particles comprises a carbon-coated layer covering the inner core; wherein the total content of the lithium-containing component in the negative electrode material particles is 0.01-10 wt.%.

[0070] In a preferred embodiment, the content of lithium in the negative electrode material particles is 1-5 wt.%; optionally, the content of Li2O is 50-100 wt.% based on the total amount of lithium in the negative electrode material.

[0071] In a preferred embodiment, the content of the carbon-coated layer in the negative electrode material particles is 5-50 wt.%, preferably 15-50 wt.%.

[0072] In a more preferred embodiment, the lithium-containing component does not contain metallic lithium. The present disclosure controls the absence of lithium in metallic form in the negative electrode material particles, which can have the effect of improving the stability of the lithium-containing silicon-based negative electrode material and reducing the pH value of the lithium-containing silicon-based negative electrode material slurry. The test method of the present disclosure, which detects whether bubbles are generated by immersing the lithium-containing silicon-based negative electrode material in water for 24 to 72 hours, can prove that the low-lithium-content silicon-based negative electrode material particles do not contain lithium in metallic form. In the present disclosure, "the lithium-containing component does not contain metallic lithium" means that the content of lithium in metallic form is 0.005% by weight or less, based on the total weight of lithium elements in the negative electrode material particles.

[0073] In an embodiment, the average particle size of the negative electrode material particles is 0.2 to 50 μm, the average pore size is 1 to 50 nm, and the BET specific surface area is 0.5 to 100 m 2 / g; preferably, the average particle size of the negative electrode material particles is 0.5 to 10 μm, the average pore size is 5 to 20 nm, and the BET specific surface area is 1 to 5 m 2 / g.

[0074] In an embodiment, the thickness of the carbon coating layer in the negative electrode material particles is 1 to 500 nm, and preferably 10 to 100 nm.

[0075] The fourth aspect of the present disclosure provides a negative electrode of a lithium ion battery, which comprises the low-lithium-content silicon-based negative electrode material of the second or third aspect of the present disclosure.

[0076] According to the present disclosure, the negative electrode of the lithium ion battery can be prepared by a method known in the art. For example, the negative electrode is obtained by coating a slurry, which comprises the negative electrode material provided by the present disclosure, a conductive agent, a binder, and the like, wherein the conductive agent and the binder are selected conventionally in the art.

[0077] The fifth aspect of the present disclosure provides a lithium ion battery, which comprises the low-lithium-content silicon-based negative electrode material of the second or third aspect of the present disclosure or the negative electrode of the fourth aspect of the present disclosure.

[0078] According to the present disclosure, the lithium ion battery can be assembled by a method known in the art.

[0079] The present disclosure is further illustrated by the following examples, but the present disclosure is not limited in any way by the examples.

[0080] In the following examples, the raw materials used are commercially available products, unless otherwise specified.

[0081] In the following examples, the specific test methods are as follows:

[0082] The test method for the total content of the lithium-containing component in the negative electrode material particles is calculated based on the amount of added metallic lithium.

[0083] The testing method of the content of the carbon coating layer in the negative material particle is thermogravimetric differential thermal analysis, and the instrument model is STA300;

[0084] The testing method of the thickness of the carbon coating layer in the negative material particle is: the negative material particle is tested by TEM at any magnification, the thickness of the carbon material is measured at any 15 points and the average value is calculated; the instrument used is JEM-2100;

[0085] The testing method of the average particle size is a light particle size analyzer, and the instrument model is Mastersizer 3000;

[0086] The testing method of SEM is a scanning electron microscope, and the instrument model is S4800 of Japan Hitachi Company;

[0087] The testing method of XRD is an X-ray diffractometer, and the instrument model is X'Pert PRO type powder X-ray diffractometer of PANalytical Company;

[0088] The testing method of XPS is an X-ray photoelectron spectrometer, and the instrument model is VG ESCALAB;

[0089] The testing method of electrochemical cycle performance is a blue electric test system, and the instrument model is CT3001A.

[0090] Preparation Example 1

[0091] The present preparation example is used to illustrate the method for preparing micron silicon, which comprises the following steps:

[0092] The aluminum alloy with a silicon content of 60wt% (average particle size of 30-50μm) is reacted with an excess of 1mol / L HCl at 25℃ for 10h; after sufficient reaction, it is washed with deionized water until neutral, and dried in a vacuum oven at 60℃ for 12 hours to obtain micron silicon (porous silicon-containing powder A). -1 Etching with hydrochloric acid at 25℃ for 10h; after sufficient reaction, it is washed with deionized water until neutral, and dried in a vacuum oven at 60℃ for 12 hours to obtain micron silicon (porous silicon-containing powder A).

[0093] The average particle size of the porous silicon-containing powder is 2.96μm, the average pore size is 8.1nm, and the BET specific surface area is 2.21m 2 / g.

[0094] Preparation Example 2

[0095] The present preparation example is used to illustrate the method for preparing carbon-silicon composite material, which comprises the following steps:

[0096] The elemental silicon with an average particle size of 30-100 microns is added into an isopropyl alcohol solution to prepare a mixture with a solid content of 30 wt%, and 20 wt% of citric acid (based on the weight of the elemental silicon) is added. After sand milling for 32 hours, spray drying is performed to obtain a silicon-carbon composite precursor. High-temperature calcination at 800°C for 3h is performed to obtain a silicon-carbon composite (porous silicon-containing powder B).

[0097] The average particle size of the porous silicon-containing powder is 1.82 microns, the average pore size is 9.86 nm, and the BET specific surface area is 3.27 m 2 / g.

[0098] The following examples are used to illustrate the preparation of a low-lithium-content silicon-based negative electrode material for a lithium ion battery.

[0099] In the following examples and comparative examples, the inert atmosphere is an argon atmosphere.

[0100] Example 1

[0101] In an inert environment free of water and oxygen, 5g of micron-sized silicon obtained in Preparation Example 1 and 0.1g of lithium ingot (lithium to micron-sized silicon mass ratio of 1:50) are placed in a zirconia ball mill jar, which is then sealed and transferred to a planetary ball mill. The ball-to-material ratio is 20:1, the zirconia ball diameters are 5.5mm, 3.0mm, and 2.0mm, and the ratio is 2:5:3. The ball milling speed is 500rpm, and the ball milling time is 12 hours. Then, 1g of natural graphite is added for further ball milling (lithium to solid dispersant mass ratio of 1:10), and the ball milling speed is 450rpm. The ball milling time is 2 hours. Then, 1g of pitch powder is added for further ball milling (lithium to carbon source mass ratio of 1:10), and the ball milling speed is 350rpm. The ball milling time is 2 hours. The silicon-containing composite precursor is obtained by discharging. The lithium-containing silicon-based composite precursor is placed in a tube furnace under an argon atmosphere for thermal stabilization sintering. The calcination process is as follows: first, the temperature is increased to 350°C at a rate of 2°C / min, and then the temperature is kept constant for 2h for pre-stabilization. Then, the temperature is increased to 800°C at a rate of 5°C / min, and then the temperature is kept constant for 2h. After the temperature is reduced to room temperature, the low-lithium-content silicon-based negative electrode material is obtained by discharging, which is denoted as C1.

[0102] Figure 1 FIG. 1 is a SEM image of the low-lithium-content silicon-based negative electrode material C1 prepared in Example 1. As can be seen from the figure, the low-lithium-content silicon-based negative electrode material is in the form of spherical particles with good dispersibility, and the average particle size is 1-3 microns. The surface structure is relatively smooth, indicating that a relatively dense carbon coating film is formed on the surface.

[0103] Figure 2is a TEM image of the low lithium content silicon-based negative electrode material C1 prepared in this embodiment 1. As can be seen from the figure, the low lithium content silicon-based negative electrode material is a core-shell structure, the inside is a silicon material, a layer of lithium oxide layer is formed on the surface of lithium, and the outside is coated with a relatively dense carbon coating film.

[0104] Figure 3 is an X-ray diffraction pattern of the lithium-containing silicon-based material C1 prepared in this embodiment 1. As can be seen from the figure, the product is mainly silicon and carbon, and obvious lithium oxide diffraction peaks also appear, and no metal lithium and silicon-lithium alloy appears, indicating that lithium is introduced into the silicon-based material, and lithium reacts with the oxide layer on the surface of silicon during the preparation process to form lithium oxide.

[0105] Figure 4 is a Li 1s X-ray photoelectron high-resolution scanning spectrum of the lithium-containing silicon-based material C1 prepared in this embodiment 1. As can be seen from the figure, the product has obvious Li characteristic peaks, further indicating that lithium is successfully introduced into silicon, and the pre-lithium of the silicon-based material is achieved. Combined with the X-ray diffraction pattern in Figure 3 , it can be shown that the lithium in the negative electrode material exists in the form of lithium oxide.

[0106] Embodiment 2

[0107] Under anhydrous and anaerobic inert environment, 2g of micron silicon and 0.02g of metal lithium ingot (lithium to micron silicon mass ratio is 1:100) prepared in the preparation example were placed in a zirconium oxide ball mill jar, sealed and transferred to a planetary ball mill for ball milling. The ball-to-material ratio of ball milling was 20:1, the zirconium ball diameter was 5.5mm, 3.0mm and 2.0mm, the ratio was 2:5:3, the ball milling speed was 500rpm, and the ball milling time was 12 hours. Then 1g of artificial graphite was added for further ball milling (lithium to solid dispersant mass ratio was 1:50), the ball milling speed was 450rpm, and the ball milling time was 2 hours. Then 1g of pitch powder was added for further ball milling (lithium to carbon source mass ratio was 1:50), the ball milling speed was 350rpm, and the ball milling time was 2 hours. The silicon-based composite material precursor containing lithium was obtained by discharging. The lithium-containing silicon-based composite material precursor was placed in a tube furnace under argon atmosphere for thermal stabilization sintering. The calcination process was first heated to 400℃ at a rate of 2℃ / min, preheated for 1h for thermal stabilization, then heated to 800℃ at a rate of 5℃ / min, and kept for 2h. After cooling to room temperature, the low lithium content silicon-based negative electrode material was discharged and recorded as C2.

[0108] Comparative Example 1

[0109] A similar preparation method and process condition as in embodiment 2 were used, and the only difference from embodiment 2 was that no metal lithium was added (no pre-lithium), and the rest of the process was the same as in embodiment 2. A carbon-silicon composite material was prepared and recorded as DC1.

[0110] Comparative Example 2

[0111] Using a similar preparation method and process conditions as in Example 2, the only difference from Example 2 is that only lithium metal ingots are added, and natural graphite (solid dispersant) and pitch powder (carbon source) are not added. The rest of the process is the same as in Example 2, and a lithium-containing silicon-carbon composite material, denoted as DC2, is prepared.

[0112] Example 3

[0113] In an anhydrous and oxygen-free inert environment, 10g of micron-sized silicon and 0.2g of lithium metal ingots (lithium to micron-sized silicon mass ratio of 1:50) obtained in the preparation example were weighed and placed in a zirconia ball mill jar. After sealing, the jar was transferred to a nanoball mill for ball milling. The ball-to-material ratio was 20:1, and the diameters of the zirconia balls were 5.5mm, 3.0mm, and 2.0mm, with a ratio of 2:5:3. The ball milling speed was 900 rpm, and the ball milling time was 48 hours. Then, 1g of artificial graphite was added and ball milling continued (lithium to solid dispersant mass ratio of 1:5). The ball milling speed was 450 rpm, and the ball milling time was 2 hours. Then, 1g of pitch powder was added and ball milling continued (lithium to carbon source mass ratio of 1:5). The ball milling speed was 350 rpm, and the ball milling time was 2 hours. The silicon-based composite material precursor was obtained by discharging the material. The lithium-containing silicon-based composite precursor was placed in a tube furnace under an argon atmosphere for thermal stabilization sintering. The calcination process involved first heating to 350°C at a rate of 2°C / min and holding at that temperature for 3 hours for preheating and stabilization, followed by heating to 900°C at a rate of 5°C / min and holding at that temperature for 2 hours. After cooling to room temperature, the low-lithium-content silicon-based anode material, denoted as C3, was obtained.

[0114] Example 4

[0115] In an inert environment without water and oxygen, 2 g of silicon-carbon composite material obtained in the preparation example and 0.02 g of lithium sheet (lithium to silicon-carbon composite material mass ratio of 1:100) were weighed and placed in a zirconium oxide ball mill jar, which was sealed and transferred to a nano ball mill for ball milling. The ball-to-material ratio of ball milling was 20:1, the zirconium ball diameters were 5.5 mm, 3.0 mm and 2.0 mm, the ratio was 2:5:3, the ball milling speed was 300 rpm, and the ball milling time was 10 hours. Then 1 g of artificial graphite was added for further ball milling (lithium to solid dispersant mass ratio of 1:50), the ball milling speed was 350 rpm, and the ball milling time was 2 hours. Then 1 g of pitch powder was added for further ball milling (lithium to carbon source mass ratio of 1:50), the ball milling speed was 350 rpm, and the ball milling time was 2 hours. The lithium-containing silicon-carbon composite material precursor was obtained by discharging. The lithium-containing silicon-carbon composite material precursor was placed in a tube furnace under an argon atmosphere for thermal stabilization sintering. The calcination process was first heated to 350°C at a rate of 2°C / min, preheated and stabilized for 2 h, then heated to 800°C at a rate of 5°C / min, and held for 2 h. After cooling to room temperature, the lithium-containing silicon-carbon negative electrode material was discharged and recorded as C4.

[0116] Example 5

[0117] The same preparation method and process conditions as in Example 1 were used, except that in the thermal stabilization sintering process, the calcination process was first heated to 350°C at a rate of 1°C / min, preheated and stabilized for 2 h, then heated to 800°C at a rate of 3°C / min, and held for 2 h. After cooling to room temperature, the lithium-containing silicon-carbon negative electrode material was discharged and recorded as C5.

[0118] Example 6

[0119] The same preparation method and process conditions as in Example 1 were used, except that:

[0120] A one-step sintering method was used for thermal stabilization treatment. The lithium-containing silicon-based composite material precursor was placed in a tube furnace under an argon atmosphere for thermal stabilization sintering. The calcination process was heated to 800°C at a rate of 2°C / min, and held for 2 h. After cooling to room temperature, the low-lithium-content silicon-based negative electrode material was discharged and recorded as C6.

[0121] Example 7

[0122] The same preparation method and process conditions as in Example 1 were used, except that:

[0123] 2 g of micron-sized silicon and 0.1 g of lithium ingot (lithium to micron-sized silicon mass ratio of 1:20) were weighed;

[0124] Continue ball milling with 10 g of natural graphite (lithium to solid dispersant mass ratio of 1:100);

[0125] Continue ball milling with 10 g of pitch powder (lithium to carbon source mass ratio of 1:100);

[0126] A low-lithium-content silicon-based negative electrode material was obtained, denoted as C7.

[0127] Comparative Example 3

[0128] The silicon-carbon composite material (porous silicon-containing powder B) prepared in Preparation Example 2 was directly used as a negative electrode material, denoted as DC3.

[0129] The component content and structure parameters of the products obtained in the above examples and comparative examples are listed in Table 1 below.

[0130] Table 1

[0131]

[0132] Test Example

[0133] This test example is used to illustrate the electrochemical performance of the products obtained in the examples and comparative examples when used as negative electrodes of lithium ion batteries.

[0134] The products obtained in the examples and comparative examples were used as negative electrodes to assemble batteries, and their electrochemical performance was tested, with the specific steps as follows:

[0135] (1) Slurry preparation: the negative electrode material, conductive agent, and binder were weighed at a ratio of 8:1:1, and solvent water was added to adjust the slurry viscosity, and stirred for 3-5 h.

[0136] (2) Coating: the slurry was coated on a copper foil current collector using a doctor blade mold.

[0137] (3) Drying: dried in a vacuum drying oven at 120°C for 12 h.

[0138] (4) Cutting: cut into circular battery negative electrode pieces with a diameter of 15 mm, weighed, and placed in a drying oven.

[0139] (5) Assembly: assembled into CR2025 button batteries with lithium pieces as the counter electrode in a glove box.

[0140] The electrolyte was a 1M LiPF6 / EC:DMC (1:1, vol) mixture, and the separator was a Celgard 2300 polypropylene microporous membrane.

[0141] The sealed battery was allowed to stand for 24 h, and then subjected to charge-discharge test and cycle performance test using a Land battery performance test system. The test results are shown in Table 2.

[0142] Table 2

[0143]

[0144] wherein, Figure 5 is the electrochemical capacity-voltage test result of lithium-containing silicon-based material C2 prepared in Example 2 as a negative electrode to assemble a lithium ion battery, and the first coulombic efficiency is 87.58%, indicating that the negative electrode material provided by the present disclosure can have a higher first coulombic efficiency. Figure 7 is the electrochemical capacity-voltage result of silicon-carbon composite material DC1 (without pre-lithiation) in Comparative Example 1, and the specific discharge capacity of silicon-carbon composite material DC1 is 2730.0 mAh / g, the specific charge capacity is 1152.0 mAh / g, and the first coulombic efficiency is only 40.20%. Compared with DC1, the first coulombic efficiency of the battery made of the lithium-containing silicon-based material C2 obtained by the method provided by the present disclosure is greatly improved after simple powder pre-lithiation.

[0145] Figure 6 is the electrochemical cycle performance capacity retention test result of lithium-containing silicon-carbon material C4 prepared in the present Example 4 and carbon-silicon composite material DC3 without pre-lithiation in Comparative Example 3 as the negative electrode material of the battery to assemble a battery, and the test current density is 0.2C. DC3 directly uses silicon-carbon composite material as the negative electrode material without pre-lithiation, and the capacity retention rate of DC3 after 160 cycles is only 19%. Compared with DC3, it can be seen that the cycle stability of the silicon-carbon composite material C4 obtained in Example 4 is significantly improved after pre-lithiation.

[0146] Comparing C1 with C5, it can be seen that the sintering process conditions in the preparation process of Example 5 are within the range defined in the preferred embodiment of the present disclosure, and the lithium-containing silicon-carbon negative electrode material C5 prepared in Example 5 has higher first coulombic efficiency and cycle retention rate.

[0147] Comparing C1 with C6, it can be seen that the negative electrode material C1 obtained by adopting the segmented sintering treatment in Example 1 has higher first coulombic efficiency and cycle retention rate. Comparing C1 with C7, it can be seen that the C1 obtained by preparing the negative electrode material according to the mass ratio of metal lithium to silicon-containing powder as 1:(50-100), the mass ratio of solid dispersant to metal lithium as (5-50):1, and the mass ratio of metal lithium to carbon source as 1:(5-50) in the preparation process of Example 1 has higher first coulombic efficiency and cycle retention rate.

[0148] And, by comparing C1-C7 with DC2 (only adding metal lithium, without carbon layer coating), it can be seen that C1-C7 is carbon layer coated in the preparation process, no bubbles are generated in the pulping process, while DC2 is not carbon layer coated, bubbles are generated in the pulping process, which indicates that the negative electrode material prepared by the method provided in the present disclosure is coated by carbon layer, and the surface is free of lithium, and no bubbles are generated.

[0149] The preferred embodiments of the present disclosure are described in detail above in combination with the drawings, but the present disclosure is not limited to the specific details in the above-described embodiments, and various simple modifications can be made to the technical solutions of the present disclosure within the technical concept of the present disclosure, and these simple modifications all belong to the protection scope of the present disclosure.

[0150] In addition, it should be noted that each specific technical feature described in the above specific embodiments can be combined in any appropriate manner without contradiction, and in order to avoid unnecessary repetition, the present disclosure will not further describe various possible combinations.

[0151] In addition, various different embodiments of the present disclosure can also be combined in any manner, as long as it does not deviate from the idea of the present disclosure, and it should also be considered as disclosed in the present disclosure.

Claims

1. A method for preparing a low-lithium-content silicon-based negative electrode material, characterized in that, The method comprises the following steps: S1, mixing metal lithium and porous silicon-containing powder, and then performing solid-phase homogenization treatment under inert atmosphere to obtain a first mixture; wherein the mass ratio of metal lithium to porous silicon-containing powder is 1: (50-100); the porous silicon-containing powder comprises one of micron silicon powder or silicon-carbon composite material powder; S2, adding a solid dispersant into the first mixture for dispersion homogenization treatment to obtain a second mixture; the solid dispersant is selected from one or more of natural graphite, artificial graphite, mesocarbon microbeads, hard carbon and soft carbon; S3, adding a carbon source into the second mixture for carbon-coated homogenization treatment to obtain a low-lithium-content silicon-based negative electrode material precursor; S4, performing sintering treatment on the low-lithium-content silicon-based negative electrode material precursor; the sintering treatment comprises first-stage sintering and second-stage sintering, the temperature of the first-stage sintering is 200-500°C, and the temperature of the second-stage sintering is 600-1200°C; Steps S1-S4 are performed under inert atmosphere.

2. The method of claim 1, wherein, In step S1, the average particle size of the porous silicon-containing powder is 0.2-50 μm, the average pore size is 1-50 nm, and the BET specific surface area is 0.5-100 m 2 / g.

3. The method of claim 1, wherein, In step S1, the metal lithium is selected from one or more of lithium ingot, lithium wire, lithium powder and lithium sheet.

4. The method of claim 1, wherein, In step S1, the micron silicon powder is prepared by acid etching of a silicon alloy raw material; wherein the silicon alloy raw material is selected from any one or more of silicon-aluminum alloy, silicon-iron alloy and silicon-magnesium alloy, and the average particle size of the silicon alloy raw material is 1-500 μm; the acid is selected from one or more of hydrochloric acid, nitric acid and sulfuric acid.

5. The method of claim 1, wherein, In step S1, the silicon-carbon composite material is obtained by mechanically mixing elemental silicon, a solvent and an acid, and then high-temperature calcination; wherein the solvent is selected from one or more of isopropyl alcohol, ethanol, hexane, cyclohexane and acetone; the acid is selected from one or more of citric acid, hydrochloric acid, nitric acid and sulfuric acid; the average particle size of the elemental silicon is 30-100 μm; The mechanical mixing is performed by sand mill for 4-48 hours; the high-temperature calcination is performed under the conditions of a temperature of 600-1200°C and a time of 2-8 hours.

6. The method of claim 1, wherein, In step S1, the solid-phase homogenization treatment is performed by mechanical homogenization, and the mechanical homogenization is selected from any one of a ball mill, a sand mill, a homogenizer or a disperser.

7. The method of claim 6, wherein, In step S1, the rotation speed of the solid-phase homogenization treatment is 300-2000 r / min, the homogenization time is 6-72 h, and the ball-to-material ratio is (1-20):

1.

8. The method of claim 1, wherein, In step S2, the mass ratio of the solid dispersant to the metal lithium is (5-100):

1.

9. The method of claim 8, wherein, In step S2, the mass ratio of the solid dispersant to the metal lithium is (5-50):

1.

10. The method of claim 1, wherein, In step S2, the dispersion homogenization treatment is performed by mechanical homogenization, and the mechanical homogenization is selected from any one of a ball mill, a sand mill, a homogenizer or a disperser; The rotation speed of the dispersion homogenization treatment is 50-500 r / min, the time is 0.5-12 h, and the ball-to-material ratio is (1-50):

1.

11. The method of claim 1, wherein, In step S3, the carbon source is selected from one or more of a polymer carbon source, a petroleum carbon source, a sugar carbon source, a graphite carbon source and other carbon sources; The polymer carbon source includes one or more of phenolic resin, epoxy resin, polyvinylpyrrolidone and polyvinyl alcohol; The petroleum carbon source includes one or more of pitch, petroleum coke and needle coke; The sugar carbon source includes one or more of glucose, sucrose and fructose; The graphite carbon source includes one or both of natural graphite and artificial graphite; The other carbon source includes one or more of mesocarbon microbeads, hard carbon and soft carbon; The mass ratio of the metal lithium to the carbon source is 1: (5-100).

12. The method of claim 11, wherein, In step S3, the mass ratio of the metal lithium to the carbon source is 1: (5-50).

13. The method of claim 1, wherein, In step S3, the carbon-coated homogenization treatment is in the form of mechanical homogenization, which is selected from any one of a ball mill, a sand mill, a homogenizer or a disperser; The carbon-coated homogenization rotation speed is 100-500 r / min, the time is 0.5-12 h, and the ball-to-material ratio is (10-30):

1.

14. The method of claim 1, wherein, In step S4, the temperature of the first-stage sintering is 300-450℃, the temperature rising rate is 1-1.5℃ / min, and the constant temperature time is 2-4 h; the temperature of the second-stage sintering is 700-900℃, the temperature rising rate is 2-5℃ / min, and the constant temperature time is 2-5 h.

15. The method of claim 14, wherein, The inert atmosphere contains one or more of nitrogen, helium, neon, argon, krypton and xenon; the water content of the inert atmosphere is 0.1% by weight or less, and the oxygen content is 0.1% by weight or less.

16. The method of claim 1, wherein, 17. A low-lithium-content silicon-based negative electrode material prepared by the method of any one of claims 1-16. The negative electrode material includes negative electrode material particles having a core-shell structure, the inner core of the negative electrode material particles includes a porous silicon matrix and a lithium-containing component dispersed on the surface of the silicon matrix, the lithium-containing component contains Li2O; the outer shell of the negative electrode material particles includes a carbon-coated layer covering the inner core; wherein the total content of the lithium-containing component in the negative electrode material particles is 0.01-10% by weight.

18. The low-lithium-content silicon-based anode material of claim 17, wherein, The total content of the lithium-containing component in the negative electrode material particles is 1-5% by weight; 19. The low-lithium-content silicon-based anode material of claim 18, wherein, The content of the carbon-coated layer in the negative electrode material particles is 5-50% by weight. The content of the carbon-coated layer in the negative electrode material particles is 15-50% by weight.

20. The low-lithium-content silicon-based anode material of claim 19, wherein, The lithium-containing component does not contain metallic lithium.

21. The low-lithium-content silicon-based anode material of claim 19, wherein, The low-lithium-content silicon-based negative electrode material of any one of claims 17-22.

22. The low-lithium content silicon-based anode material of claim 18, wherein, The average particle size of the negative electrode material particle is 0.2-50 μm, the average pore size is 1-50 nm, the BET specific surface area is 0.5-100 m 2 / g; and the thickness of the carbon coating layer is 1-500 nm.

23. A negative electrode for a lithium-ion battery, characterized by comprising: The negative electrode of claim 23.

24. A lithium-ion battery, characterized by, ​

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